Investigation of fifteen popular and widely grown Indian rice varieties for variations in straw fodder traits and grain-straw relationships

Abstract

Fifteen 15 popular rice cultivars were investigated over two years for grain yield (GY) and straw yield (SY), harvest indices (HI), straw nitrogen content (N), neutral (NDF) and acid (ADF) detergent fiber, acid detergent lignin (ADL), Silica, in vitro organic matter digestibility (IVOMD) and metabolizable energy (ME) content. Except for ADL (P = 0.06) highly significant (P < 0.0001) differences were observed for all traits. The observed cultivar-depend variations were substantial with GY varying by 1.8-fold and SY by 2.3-fold and HI by 1.6-fold. Important straw fodder quality traits such straw N varied by 1.5-fold and the cultivar with the highest IVOMD differed from the poorest one by 6.1 percentage points. With the exceptions of N and ADL, year had a significant effect on traits. Broad sense heritability (H2) for SY and IVOMD were substantial (>0.73) and intermediate (>0.49) for GY, NDF, ADF and ME and poor (<0.17) for Silica, N and ADL.Possible trade-offs between traits were investigated. GY and SY were unrelated (P = 0.52). Nitrogen content of rice straw tended (P = 0.08) to be inversely related with GY but not with SY (P = 0.89). NDF content was unrelated to GY (P = 0.52) but was significantly (P = 0.01) positively correlated with SY. The reverse was observed for ADF, which was significantly (P = 0.02) positively correlated with GY but unrelated to SY (P = 0.48). ADL was not correlated (P = 0.79) with GY but was positively associated (P = 0.01) with SY. Silica content was also unrelated (P = 0.17) to GY but was inversely (P = 0.03) associated with SY. IVOMD and GY were inversely associated (P = 0.07) as was ME and GY (P = 0.09. IVOMD tended (P = 0.1) to also inversely related to SY but ME and SY were not related (P = 0.24). To summarize, considerable cultivars-dependent variations in food and fodder traits exist among released cultivars, though key positive straw quality traits could inversely (P < 0.10) associated with GY. Straw storage influenced straw quality, though an unexpected one since quality tended to improve. Key straw quality traits at harvest and after storage were still significantly correlated but the correlation coefficients could fall substantially below 1.